The present invention relates to image filtering to reduce noise in an image, and more particularly, to 3D image filtering based on volume rendering to suppress noise and enhance structure of interest in a 3D image.
Image noise is inherent to any imaging device. Image noise in a volumetric image presents undesirable artifacts. Existing noise reduction and image enhancement methods do not totally solve this problem. Accordingly, better noise reduction and image enhancement algorithms are desirable.
Conventional noise reduction methods are mostly based on signal processing theories. A smoothing filter convolves the original image with a mask that represents a low-pass filter or smoothing operation. However, smoothing filters tend to blur the image. The anisotropic diffusion method solves a smoothing partial differential equation similar to a heat equation to remove noise without blurring the edges of the image. A median filter is an example of a non-linear filter and, if properly designed, is very good at preserving image detail. However, median filters work better for salt-and-pepper image noise.